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// Another example from issue #84660, this time weaponized as a safe transmute: an opaque type in an
// impl header being accepted was used to create unsoundness.
//@ revisions: current next
//@ ignore-compare-mode-next-solver (explicit revisions)
//@[next] compile-flags: -Znext-solver
#![feature(type_alias_impl_trait)]
trait Foo {}
impl Foo for () {}
type Bar = impl Foo;
fn _defining_use() -> Bar {}
trait Trait<T, In> {
type Out;
fn convert(i: In) -> Self::Out;
}
impl<In, Out> Trait<Bar, In> for Out {
type Out = Out;
fn convert(_i: In) -> Self::Out {
//[next]~^ ERROR: cannot satisfy `Bar == _`
//[current]~^^ ERROR: item does not constrain `Bar::{opaque#0}`, but has it in its signature
unreachable!();
}
}
impl<In, Out> Trait<(), In> for Out {
//~^ ERROR conflicting implementations of trait `Trait<Bar, _>`
type Out = In;
fn convert(i: In) -> Self::Out {
i
}
}
fn transmute<In, Out>(i: In) -> Out {
<Out as Trait<Bar, In>>::convert(i)
}
fn main() {
let d;
{
let x = "Hello World".to_string();
d = transmute::<&String, &String>(&x);
}
println!("{}", d);
}
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